Alloy



Patented July 4, 1933 UNITED. STATES PATENT; OFFICE FREDERICK M. BEOKET, OF NEW YORK, N. Y., ASSIGNOR '10 METALLURGICAL COMPANY, A. CORPORATION OF WEST VIRGINIA ALLOY No Drawing.

The invention comprises a group of substantially nickel-free alloys which contain iron as the preponderating constituent, and which also contain chromium, manganese and molybdenum as essential constituents.

In my application Serial N 0. 435,957, filed March 14, 1930, I have shown that ferrous alloys containing sufiicient chromium, say to 22%, to render them strongly resistant to corrosion, can be advantageously modified by adding manganese, so t at the manganese content of the complete alloy Wlll I fall, for example, between 6% and 16%. It

has heretofore become an extensive practice to modify corrosion-resistant binary ironchromium alloys by incorporating nickel, but the addition of nickelimpairs the resistance of the alloy to the action of sulphur-bearing gases. Manganese gives the high degree of workability and the other properties imparted by nickel, but without evoking susceptibility to attack by sulphur-containing gases.

1 have now discovered that if both manganese and molybdenum are added to a corrosion-resistant iron-chromium base, the alloys produced have properties especially adapting them to certain uses. Articles fabricated from these new alloys resist corrosion at elevated temperatures at least as well as the ternary iron-chromium-manganese alloys; while the strength at elevated temperatures is materially enhanced by the presence of the molybdenum.

The invention is not restricted to the incorporation of any particular proportion of molybdenum. Doubtless very small additions of molybdenum produce an efi'ect, but it is my present opinion that at least 1% will be required, as a ,rule, "to impart the desired qualities. Also, the quantity added will usually not exceed 10%, but useful alloys can certainly be made with higher percentages Application filed May 18, 1980. Serial No. 452,131.

imparted by the incorporation of more carbon, and without much impairment of the stain-resistance and workability, but for the applications of the alloy herein contemplated, the carbon is preferably held below a maximum of about 0.3%.

The effect of molybdenum is particularly advantageous when the alloy is used at temperatures materially below 900 C. There are many fields of use in which the temperatures encountered are in the vicinity of 600 (1., and at such temperatures the molybdenum-containing alloys are decidedly stronger than similar alloys free from this metal. The merit of the new alloys in this respect is best illustrated by measurements of yield point made at 600 0., and typical numbers are shown in the following table Among the more important fields of use for the new alloys may be mentioned the fabrication of tubes for the pyrolysis or crackng of hydrocarbon material, e. g. the crackmg of petroleum fractions for the manufacture of gasolene; and the construction of supporting structures for such tubes.

I claim:

1. A ferrous alloy characterized by high resistance to sulphur-containing gases and by high strength at elevated temperatures in the vicinity of 600 (1, and which has substantially the composition: chromium from about 16% to about 22%,.manganese from about 6% to about 16%, molybdenum from about 1% to about 10%, and carbon, the carbon content being less than about 0.3%, the balance being iron. 1

2 A ferrous alloy characterized by high resistance to sulphur-containing gases and by high strength at elevated temperatures 1n the vicinity of 600 0., and which has substantially the composition: about 18% of chromium, about 8% of manganese, from about 1% to about 10% of molybdenum, and carbon, the carbon content bemg less than about 0.3%, the balance being iron.

3. A ferrous alloy characterized by high resistance to sulphur-containing gases and by high strength at elevated temperatures in the vicinity of 600 C., and which has substantially the composition: chromium from about 16% to about 22%, manganese from about 6% to about 16%., molybdenum from about 3% to about 10%, and carbon, the carbon content being less than about 0.3%, the remainder iron.

4. A ferrous alloy characterized by high resistance to sulphur-containing gases and b high strength at elevated temperatures in tlie vicinity of 600 (3., and which has substantially the composition: chromium from about 16% to about 22%, manganese from FREDERICK M. BECKET. 

